This invention relates to a valve.
More particularly, the invention relates to a fuel-injecting valve for internal combustion engines which is provided with an axially slidable nozzle needle which is capable of being lifted off its valve seat by the pressure of the fuel with the nozzle body being formed with a spray hole disposed in the nozzle body at an acute angle relative to the nozzle axis.
An injector of this type is disclosed in German Patent Application P 2746 010.2. The injector according to that disclosure has the nozzle needle formed with a point below the valve seat which penetrates into the spray hole at least in the closed and partially closed positions, so that the free cross-sectional area of the spray hole is smaller than the free cross-sectional area at the valve seat in nearly all positions of the nozzle needle.
The purpose of this combination is to provide control of the free cross-sectional area at the valve seat together with simultaneous control of the free cross-sectional area directly at the spray hole; this assures that fuel pressure at the spray hole is available substantially undiminished throughout the complete injection cycle. As a result, mixture formation and, consequently, combustion, are improved in all operating modes of the engine, especially in the low speed and low load modes. Futhermore, there is and improvement in exhaust gas quality and a reduction of fuel consumption.
Further essential factors for the quality of mixture formation in the combustion chamber of an internal combustion engine are the fuel jet orientation, the fuel jet characteristics, as well as the utilization of the kinetic energy at the valve seat.
It has been well known in the art for a long time that it is most advantageous during starting as well as in the low load and/or speed ranges of the engine to have a relatively high degree of direct contact fuel/air mixing which is obtainable by increased atomization of the fuel spray and a spray orientation directed directly into the combustion chamber air for combustion, whereas a compact fuel jet positioned in a direction closer to the combustion chamber wall is desirable in the upper load and/or speed ranges in order to prevent dangerous peak pressures as a result of combustion proceeding at too fast a rate. This applies especially to internal combustion engines which employ the method of wall deposition of the fuel, for which purpose a change in direction of the fuel spray or jet is most advantageous.
With a view to meeting these requirements, a number of proposals have been made which, however, all suffered from one drawback or other. For instance, the German Pat. No. 1,014,382 suggested a device for deflecting the fuel spray where a guiding element adapted to be adjusted as a function of the temperature is provided in the region of the fuel spray. This guiding element consists of a bimetallic or similar device and is designed to deflect the fuel towards the center of the combustion chamber while the combustion chamber is cold, whereas the fuel is guided towards the wall when the combustion chamber is warm. This device is strictly temperature-dependant while the fuel spray pattern and the injection pressure are not taken into account. Furthermore, it is most vulnerable to malfunctions.
Alternative proposals whereby the injector is rotated to suit the various load ranges of the engine have failed to find acceptance due to their complexity.